In what may one day be remembered as a defining moment in our search for life beyond Earth, astronomers have uncovered compelling evidence of biological signatures on a faraway exoplanet — signs that, until now, have only ever been associated with living organisms on our own planet.
The discovery centers on K2-18b, an ocean-rich world orbiting a red dwarf star in the Leo constellation, approximately 124 light-years from Earth. What makes this planet particularly intriguing is not just its Earth-like temperature or its position in the so-called “habitable zone”, but what its atmosphere is telling us.
Using the ultra-sensitive instruments aboard the James Webb Space Telescope (JWST), a team of scientists led by Professor Nikku Madhusudhan from the University of Cambridge has detected dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) — two sulfur-based compounds that, here on Earth, are almost exclusively produced by marine microorganisms, particularly phytoplankton.
These chemical signatures were found in concentrations thousands of times stronger than those typically present in Earth’s atmosphere — a detail that suggests something extraordinary may be occurring on K2-18b.
The implications? As per current scientific understanding, no known non-biological processes produce these molecules in such abundance. The team believes that the presence of an ocean beneath the exoplanet’s hydrogen-rich atmosphere, combined with these molecules, strengthens the case for a thriving microbial biosphere — or at the very least, complex chemical activity mimicking biological processes.
To put it simply, this is the most compelling evidence yet for potential life outside our solar system.
While these claims are not yet definitive proof of life, the findings represent a major step forward. The signals have reached a “three-sigma” level of statistical significance, which means there is just a 0.3% chance the detection happened randomly. Scientists are aiming for the more stringent five-sigma threshold to confirm it as a bona fide scientific discovery, for which they estimate another 16 to 24 hours of JWST observation time would suffice.
The atmosphere of K2-18b had already shown traces of methane and carbon dioxide in previous observations — key carbon-based molecules needed for life. Now, the independent detection of DMS and DMDS using a different JWST instrument in a separate wavelength range only deepens the mystery.
“We’ve reached a moment where the idea of a living universe no longer feels out of reach,” says Professor Madhusudhan. “This is the closest we’ve ever come to spotting the potential chemical footprints of life on another world.”
His team remains cautious, acknowledging that unknown chemical processes could also be at play. They are now working to determine whether the detected molecules could be produced abiotically, without the involvement of life.
And it’s not just K2-18b that’s raising eyebrows in the cosmic neighborhood.
In a separate breakthrough, scientists examining Martian rock samples have discovered organic molecules of unprecedented length — carbon chains up to 12 atoms long. These structures, found in rocks billions of years old, are often associated with fatty acids, key components of fats and oils that arise from biological activity on Earth.
Together, these two discoveries — on K2-18b and Mars — are fueling renewed excitement about the age-old question: Are we alone?
While we may still be a few steps away from a definitive answer, the path to it has never been clearer.
As more data pours in and telescope capabilities expand, the cosmos may finally begin to whisper its deepest secret — that life, in some form, may not be a rare miracle, but a universal truth.
